The Platypus Big Zip SL is more durable than ever and loaded with improved features. Platypus have redesigned the shutoff valve making it easier to use, and the reservoir itself is now softer and more flexible, but still taste-free. The new easy-to-clean, wide-mouth SlideLockâ„¢ closure has secondary reinforcement so you know it's sealed securely, and if you want to remove the reservoir from a pack without re-routing the hose then Platypus have provided a quick-disconnect valve to help you do just that.